Extinct Ice Age creatures such as woolly mammoths could be recreated after scientists cloned mice from frozen cells.
A team of researchers produced the clones from DNA taken from mice that had been dead for 16 years and preserved at minus 20°C. The breakthrough in Japan raises hopes of “resurrecting” bigger species such as mammoths, whose remains are sometimes found deep-frozen. Until now, Dolly the Sheep-style cloning has been achieved only by using live donor cells.Cloning from thawed-out frozen cells was thought almost impossible because of damage caused by ice crystals. But Japanese scientists thawed out the dead mice and collected nuclei from cells in their brain tissue. These were injected into empty eggs, whose own DNA had been removed, to generate cloned embryos. Stem cells taken from the embryos were then used in a second round of cloning. And this genetic material was used to produce embryos that grew into the four mouse clones.
A further nine mouse clones were created by mixing the cells of different embryos. Dr Teruhiko Wakayama, from the Centre for Developmental Biology in Kobe, Japan, said: “We have demonstrated that healthy cloned mice can be obtained by nuclear transfer — using cells from frozen bodies.”